184 DB. C. J. rORSYTH MAJOR ON MIOCENE SQinUEELS. [Feb. 28, 



3. To the Xerus-tyi^e belong most of the semi-hypsodont 

 Sfiiirme teeth of the groups already meutioued. It is dis- 

 tinguished from the Sciurus-milgaris-tyYie by a more complete 

 ]o])hodontism, the crests ruuuing in a transverse direction, and 

 the valleys being reduced to narrow but deep fissures. The main 

 difference from Ungulate lopbodout molars consists in their having 

 not two, but four or e\ en five crests, the anterior and posterior 

 margin of the molar being as much or almost as much raised as 

 the two medial crests. Wo that the A't'j'««-type presents in upper 

 as well as in lower molars three transverse depressions or fissure- 

 like valleys (and four in superior molars where there are five 

 crests). This type forms on the whole a \ery striking approach 

 to the bystricomorphan molar. 



Twenty years ago I pointed out that two Afi'ican Squirrels, 

 ;SV. conr/iciis and <S'('. Ituvostigma (this last being now considered as 

 a variety of Sc. pijrropus), approach the Hystrioomorpha in a 

 further development of the characters in wbicJi the Ethiopian 

 Xervs departs from the/SV«(«(5-i'«?(/rt/-is-type. Again, the Eocene 

 Sciiij'oidcs was shown to resemble in its molars those of the 

 Hystricomorpha Cercolahes and Eretliizon, whilst, on the other 

 hand, the Eocene bystricomorphan T)-ec7iom>/s was shown to 

 approach Sciuroides \ 



Twelve j'ears later, Schlosser, working on fossil forms, with 

 much richer material at bis command, confirmed these observations, 

 showing that a group of Tertiary Eodentia shoA^ed characters 

 intermediate between the Sciuromorpha and Hystricomorpha '". 



It is of no little interest that actually living Sciuromorpha show 

 iu their dentition, as w ell as in the characters of their skull, that 

 the distinction between Sciuromorpha and Hysti'icomorpha is less 

 sharp than is generally admitted. Schlosser seems not to have 

 examined any recent Ethiopian Squirrels, as he does not mention 

 the important characters they present. Nor has any other author, 

 with the exception of Alph. Milne-Edwards, who incidentally 

 mentions Sciums pj/rrojms, F. Cuv., saying that " les molaires 

 offrent une apparence toute particuliere, due a I'existence de replis 

 d'c'mail qui s'enfoncent profouilement dans la dentine, constituant 

 ainsi de veritables rubans. Je ne connais que cette espece sur 

 laquelle on observe ces particularites ; cependant, chez certains 

 Xervs, on en voit dea indications " ^ 



The fact is that tlie majority of Ethiopian Squirrels depart from 

 the Sciuriue type both in their superior and inferior molars, 

 ai)proaching towards bystricine lophodonty by the uniting of tlieir 

 cusps in a transverse direction, so that the characteristic cup-like 



' C. J. Forsyth Major, "Nngeruberreste aiis Bohnerzeu SiiddeutsL-blands iind 

 der Schweiz. Nebst Beitriigeu zu einer vergleichendeu Odontograpliie vou 

 ITngulaten imd Unguirulaten," ralieontographica, Bd. xxii. 1873, pp. TH-l.SO. 



^ Max Schlosser, " Die Nager des Europiiischen Tertiars ete.," Palaonto- 

 grapliiea, xxxi. 1885, pp. 10-lfi2. 



^ H. et Alph. Milne-Ednards, " Recherehes pour servir a I'lTisf oire Naturolle 

 dcs Mammiferes, ete." (Paris, 1868-1874). p. IfiO, 



